The food got to tasting all the same after 10 days
My Panama Canal cruise was 15 days and I was tired of the food too.
The NCL sounds better-with two days in each port. I know when I visited Hawaii I could have spent two days at the Polynesian Cultural Center alone.
And while I like sea days, 4 days at a stretch seems like a lot. There would have to be a lot of activities to keep the fun going.
I hope you had nice weather at least.